Vitamins are useful as nutritional supplements in the diet of various animals. Vitamins act as catalysts in nearly every biochemical pathway. For that reason vitamin deficiency leads to numerous diseases and physical ailments.
Vitamin D3 is implicated in numerous diseases. Too much or too little Vitamin D3 in the parathyroid can lead to hyperparathyroidism, hypoparathyroidism, pseudohypoparathyroidism, and secondary hyperparathyroidism. In the pancreas Vitamin D3 is implicated in diabetes. In the liver, problems with Vitamin D3 can lead to cirrhosis, and obstructive jaundice. Vitamin D3 is intimately involved in the regulation of calcium levels and in the bone is implicated in fibrogenisis imperfecta ossium, osteitis fibrosa cystica, osteomalacia, osteoporosis, osteopenia, osteosclerosis, renal osteodystrophy, and rickets. In the intestine, Vitamin D3 plays a role in glucocorticoid antagonism, idiopathic hypercalcemia, malabsorption syndrome, and tropical sprue. Psoriasis in the skin, medullary carcinoma in the thyroid, sarcoidosis in the lung, and hypophosphatemic VDRR and chronic renal disease in the kidney are all affected by the levels of Vitamin D3 in the body.
Vitamin D3 is produced by the skin under normal sunlight conditions through the oxidation of cholesterol. Vitamin D3 is then converted by the liver into 25-hydroxy Vitamin D3. Finally, 25-hydroxy Vitamin D3 is converted by the kidney into 1α,25(OH)2 Vitamin D3, which is active in various biochemical pathways.
The production of 1α,25(OH)2 Vitamin D3 is shown below.

25-hydroxy Vitamin D3 is a reservoir of the downstream 1α,25-hydroxy Vitamin D3 in the body. When the level of Vitamin D3 is adequate, 25-hydroxy Vitamin D3 is stored in the liver. It is released from the liver, as required, and further processed by the kidney into the active molecule.
For these reasons, it is useful to provide 25-hydroxy Vitamin D3 to animals as a nutritional supplement. Formulations containing 25-hydroxy Vitamin D3 are sold under the trademark HY-D (Roche Vitamins Inc., Parsippany, N.J.).
Unfortunately, 25-hydroxy Vitamin D3 is unstable under conventional storage conditions, resulting in a time-dependent loss of activity per unit mass. Among other things, 25-hydroxy Vitamin D3 is prone to oxidation, particularly during storage over extended periods of time. Such degradation can adversely affect dosing of 25-hydroxy Vitamin D3 when incorporated into animal feeds.
It would, therefore, be advantageous to provide 25-hydroxy Vitamin D3 compositions with improved stability characteristics under a wide spectrum of conditions and in combination with various nutritional additives. These and other objects of the present invention are described in greater detail below.